Grafted polymers as oleophobic low adhesion anti-wetting coatings for printhead applications

ABSTRACT

An inkjet printhead includes a front face having a polymer coating, the polymer coating including an oleophobic grafted polymer having a crosslinked fluoroelastomer and a perfluorinated polyether grafted to the crosslinked fluoroelastomer.

STATEMENT OF RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.13/931,983, filed Jun. 30, 2013, the entire contents of which areincorporated herein by reference in its entirety.

BACKGROUND

Embodiments disclosed herein relate to coatings employed on elements ofa printing apparatus. In particular, embodiments disclosed herein relateto oleophobic anti-wetting coatings employed on the front face of aprinthead.

In typical solid ink printhead configurations, a nozzle plate isprovided with an array of jets through which the ink exits a jet stack.In some printhead systems, the nozzle plate and jet stacks comprisestainless steel plates, although recently these parts have been replacedwith flexible, polymer layers such as polyimides. In some instances, thepolyimide film receives an anti-wetting coating, bonded to a stainlesssteel aperture plate, and subsequently a laser ablates the array ofapertures into the polyimide film.

Drooling nozzles, wetting and adhesion of ink on the printhead frontface lead to missing and misdirectional jetting along with poor imagequality. Drooling nozzles weep ink when the internal pressure of theprinthead exceeds a particular pressure. The higher the pressure thenozzles can maintain without weeping the better the performance. Wettingoccurs when the front face of the printhead remains wet after printing.This ink that remains on the printhead can block the nozzles resultingin missing nozzles and misdirectional printing. FIG. 1 shows aphotograph of such a contaminated printhead.

One approach to address these issues employs an active cleaning bladesystem. The system purges ink from the printhead and a wiper blade thenwipes the ink off of the front face. Ink purges typically occur afterthe system detects missing jets and after a power-down when the ink hasfrozen or solidified, shrunk and drawn air into the system. The inkpurge expels contamination, trapped air and clears the nozzles, and thenthe wipers clean off the front face.

In conjunction with wiper blade systems, various anti-wetting coatingshave been used to improve performance. Current coatings, while havinggood thermal and ink stabilities, may suffer from lower mechanicalrobustness than may be desirable, especially with the demands placed onsuch coatings when used in conjunction with wiper blade systems. Otherissues may arise due to coating stability under printhead manufacturingconditions.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a photograph of a contaminated printhead front face.

FIG. 2 shows a side view of printhead assembly.

FIG. 3 shows a side view of an intermediate structure in a process forpreparing the printhead assembly of FIG. 2, in accordance withembodiments disclosed herein.

FIG. 4 shows a side view of another intermediate structure in a processfor preparing the printhead assembly of FIG. 2, in accordance withembodiments disclosed herein.

FIG. 5 shows a side view of yet another intermediate structure in aprocess for preparing the printhead assembly of FIG. 2, in accordancewith embodiments disclosed herein.

FIG. 6 shows a synthetic procedure for making grafts.

FIG. 7 shows a thermogravimetric analysis (TGA) profile of an exemplaryoleophobic grafted polymer, in accordance with embodiments disclosedherein. The TGA analysis indicates that the coating is thermally stableup to about 330° C. without weight loss.

SUMMARY

In some aspects, embodiments disclosed herein relate to inkjetprintheads comprising a front face having a polymer coating, the polymercoating comprising an oleophobic grafted polymer comprising acrosslinked fluoroelastomer and a perfluorinated polyether grafted tothe crosslinked fluoroelastomer.

In some aspects, embodiments disclosed herein relate to processes formaking an oleophobic grafted polymer coating on a printhead comprisingcrosslinking a fluoroelastomer with an aminofunctionalized silanegrafting an alkoxysilane-terminated perfluorinated polyether to thecrosslinked fluoroelastomer to form a oleophobic grafted polymer, andcoating the oleophobic grafted polymer on a printhead front face.

In some aspects, embodiments disclosed herein relate to inkjetprintheads comprising a front face having a polymer coating, the polymercoating comprising a structure of formula I:

wherein FE is a fluoroelastomer, PFPE is a perfluorinated polyether, Lis a linker, m, and o are independently an integer from 3 to 8, n is aninteger from 1 to 10, each incidence of R¹ and R² is independently asubstituted or unsubstituted C₁-C₆ alkyl, and R³ and R⁴ areindependently an optionally fluorinated C₁-C₆ alkyl or an optionallyfluorinated C₁-C₆ alkoxy.

DETAILED DESCRIPTION

Embodiments disclosed herein provide thermally stable, mechanicallyrobust, low adhesion coatings based on oleophobic grafted polymersprepared by grafting crosslinked fluoroelastomers withperfluoropolyethers. The oleophobic grafted polymers may exhibitadvantageous and/or complementary chemistry relative to polyurethanebased coatings. In embodiments, the oleophobic grafted polymers employedas coatings may be particularly useful in high definition (HD) piezoprinthead applications where the coating is applied on the printheadfront face. Coatings (or films) of the oleophobic grafted polymersdisclosed herein may exhibit high ink contact angles (greater than 50degrees) and low sliding angles (less than 30 degrees) while havingexcellent thermal stability. In contrast to other coatings in the art,the oleophobic grafted polymers disclosed herein may produce little tono oil on the surface of the coating after curing. Moreover, suchcoatings may also exhibit minimal thickness and mass loss after exposureto temperatures in excess of 290° C., making them suitable for use understringent printhead fabrication conditions. Coatings employing theoleophobic grafted polymers disclosed herein are robust and may have along shelf life even when subjected to continual exposure totemperatures of about 140° C. in molten ink for 2 days. The oleophobicgrafted polymer coatings can be used with solid inks, pigmented inks andUV inks, and can enable good performance under high drool pressure whiledemonstrating easy clean and self-cleaning properties. Finally, theoleophobic grafted polymers can be formed into the requisite coatings bysimple flow coating techniques, facilitating printhead manufacture.These and other advantages will be apparent to those skilled in the art.

In some embodiments, there are provided oleophobic grafted polymerscomprising a crosslinked fluoroelastomer and a perfluorinated polyethergrafted to the crosslinked fluoroelastomer.

As used herein, the term “oleophobic” when used in conjunction with thegrafted polymers, refers to the physical property of the graftedpolymers to repel oils, hydrocarbons, and more generally organiccompounds, especially non-polar organic compounds. Oleophobic characterimparts anti-wetting properties that are useful to repel wetting bysolvent-based, solid inkjet based, and other pigmented and UV curableink compositions. The oleophobic character can provide the coatings withgood contact angle and sliding angle characteristics to to facilitateperformance under high drool pressure.

As used herein, the term “grafted polymer” refers to the chemicaljoining of two or more pre-fabricated polymers. Grafting can be viewedas a form of polymer crosslinking. For example, a graft polymerdisclosed herein may be prepared by reacting a pre-fabricatedfluoroelastomer with a pre-fabricated perfluorinated polyether with theaid of a crosslinking agent. In embodiments, the crosslinker employed tocrosslink the fluoroelastomer serves a dual role by providing a point ofattachment for the graft chemistry to attach the perfluorinatedpolyether.

As used herein, the term “fluoroelastomer” refers to any materialgenerally classified as an elastomer and containing a substantial degreeof fluorination. Fluoroelastomers are synthetic fluorine-containingrubberlike polymers (typically co-polymers/terpolymers) characterized byhigh thermal stability, nonflammability, and resistance to corrosivemedia. In embodiments, the fluoroelastomer (FE) has a fluorine contentof at least about 65 percent. In embodiments the fluorine content may bein a range from about 50 to about 90 percent, or about 60 to near 100percent. Exemplary commercial fluoroelastomers generally have a fluorinecontent in a range from about 66 to about 70 percent.

Fluoroelastomers currently known and available include copolymers ofvinylidene fluoride and hexafluoropropylene, terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, and alternatingcopolymers of propylene and tetrafluoroethylene. Such fluoroelastomersare available commercially as VITON™ (Dupont), DYNEON™ (3M), FLUOREL™(3M), AFLAS™ (3M), and TECNOFLON™ (Solvay Solexis) classes of products.Such fluoroelastomers may exhibit excellent solvent and oil resistanceand also have a relatively high temperature resistance compared to theirnon-fluorinated elastomer counterparts. In embodiments, thefluoroelastomer (FE) may be a polymer comprising a monomer unit selectedfrom the group consisting of vinylidene fluoride, tetrafluorethylene,hexafluoropropylene, perfluoromethylvinylether and combinations thereof.In some such embodiments, the fluoroelastomer is a terpolymer ofvinylidene fluoride, tetrafluorethylene, and hexafluoropropylene.

In embodiments, the fluoroelastomer (FE) has a molecular weight in arange from about 50,000 to about 70,000 daltons as measured by gelpermeation chromatography. In embodiments the fluoroelastomer may beselected based on its tensile strength. In some such embodiments, thetensile strength of the fluoroelastomer may be in a range from about 15mPa to about 25 mPa, or about 20 to about 25 mPa, or about 22 mPa toabout 25 mPa, as measured by the standard ASTM D412C. In embodiments,the fluoroelastomer is selected particularly for its ability toparticipate in crosslinking chemistry as disclosed herein.

As used herein, a perfluorinated polyether refers to a polyether polymerhaving a substantial degree of fluorine substitution, and may be anyfluorinated oligomer, homopolymer, or copolymer. Perfluorinatedpolyethers may exhibit comparable chemical stability to fluoroelastomersand may exhibit similar properties. In embodiments, the perfluorinatedpolyether (PFPE) is an alkoxysilane-terminated perfluorinated polyetherhaving an average molecular weight in a range from about 1,500 daltonsto about 2,500 daltons. Perfluorinated polyethers may be selected fortheir ability to bond to silanols, while having similar solventrepellent properties as the fluoroelastomers. Moreover, theperfluorinated polyether component may be selected to confer goodabrasion resistance to the oleophobic grafted polymers. Abrasionresistance is especially useful in printhead systems employing wiperblades which will continually contact the coating during use.

Suitable perfluorinated polyethers include those of the FLUOROLINK™(Solvay Solexis) class. In particular embodiments, the perfluorinatedpolyether may be bifunctionally substituted with a linker (L)terminating in an alkoxysilane as in the compound of general formula II:

Terminal alkoxysilane groups provide a chemical handle for downstreamgrafting chemistry, in accordance with embodiments disclosed herein. Thegrafting chemistry of the alkoxysilane group may be accomplished with asubstrate bearing a hydroxyl group, such as an organic alcohol or asilanol. Silanol coupling partners provide access to siloxane products(Si—O—Si), such as the oleophobic grafted polymers disclosed herein. Thelinker (L) employed in compounds of formula II may comprise anysubstituted or unsubstituted C₁-C₆ alkyl, including fluorinated alkyls,such as perfluorinated alkyls. Linker L is also may also comprise anycompetent organic functional group to attach to the main perfluorinatedpolyether chain at a terminal oxygen, or in some embodiments, to at aterminal carbon atom. Non-limiting functional groups for attachment tooxygen include carbamates, esters, ethers, and the like. The R groups ofthe alkyoxysilane moiety (Si(OR)₃) may be the same or different. R mayinclude methyl, ethyl, n-propyl, or isopropyl any of which may besubstituted, including substitution with fluorine. R may also behydrogen. In some embodiments, R is hydrogen after a hydrolysis step inpreparation for grafting chemistry. In formula II, m, n, and o areintegers that are selected based on the target molecular weight, asdescribed above. In embodiments, m and o are integers from 2 to 8. Inembodiments, n is an integer from 2 to 4.

In embodiments, the oleophobic grafted polymers disclosed herein may becompounds of formula I:

-   -   wherein FE is a fluoroelastomer,    -   PFPE is a perfluorinated polyether,    -   L is a linker,    -   m, n, and o are independently an integer from 1 to 10;    -   each incidence of R¹ and R² is independently an optionally        fluorinated C₁-C₆ alkyl,    -   R³ and R⁴ are independently an optionally fluorinated C₁-C₆        alkyl or an optionally fluorinated C₁-C₆ alkoxy. In embodiments,        m and o are independently an integer from 3 to 8 and n is an        integer from 1 to 10. In embodiments, the linker L comprises a        C₁-C₆ alkyl terminating in a functional group capable of        covalently linking to a terminal hydroxyl functionality group of        the perfluorinated polyether, as described above.

Any C₁-C₆ alkyl or C₁-C₆ alkoxy may be straight chain or branched. Inembodiments, either of these groups may be optionally substituted,including substitution with halogens other than fluorine, such aschlorine or bromine. One skilled in the art will recognize that becausestructure I is polymeric, not every site where the perfluorinatedpolyether is shown in structure I may actually be so substituted. Thus,in embodiments, the printhead coatings disclosed herein may comprise amixture of structure I and structure III:

where each of the groups are defined as set forth above. In embodiments,structure III may be a minor component and present at less than about 10percent, or less than about 5 percent, or less than about 1 percent byweight of the coating composition. In some embodiments, compounds ofstructure III, where present, may have the latent silanol groups capped.For example, they may be capped as alkoxy groups by treatment with analkylating agent.

Compounds of formula I comprise the fluorelastomers (FE) andperfluorinated polyethers (PFPE) described herein above. The two polymertypes are brought together with the aid of a crosslinker. Thecrosslinker may be used to first crosslink the fluoroelastomer withitself. In embodiments, the fluoroelastomer is crosslinked with anaminofunctionalized silane. In embodiments, the aminofunctionalizedsilane also provides the graft attachment point for the perfluorinatedpolyether, as indicated in the structure I. In embodiments, theaminofunctionalized silane may be based on end-capping of a polysiloxane(or just siloxane where n=1 in structures I and III) with 3-aminopropyltrimethoxy silane (A0800, available from UCT, Bristol, Pa.). One skilledin the art will appreciate that the crosslinking agent may itselfinclude a high degree of fluorination, although this is not necessary.

In some embodiments, there are provide processes for making anoleophobic grafted polymer comprising crosslinking a fluoroelastomerwith an aminofunctionalized silane and grafting analkoxysilane-terminated perfluorinated polyether to the crosslinkedfluoroelastomer. In some such embodiments, the oleophobic graftedpolymer accessed by such a process may comprise the compound ofstructure I, described above. In embodiments, the crosslinking step maybe performed in the presence of the alkoxysilane-terminatedperfluorinated polyether. Without being bound by theory, it is expectedthat the crosslinking of fluoroelastomer comprising hydrogen atoms inthe backbone may allow the fluoroelastomer to be dehydrofluorinated asindicated in Step 1 of reaction Scheme 1 below. Dehydrofluorinationprovides an unsaturated fluoroelastomer intermediate and a protonatedaminofucntionalized crosslinker. Regeneration of the amine with base(Step 2) and subsequent amine addition across the unsaturation (Step 3)provides a crosslinked fluoroelastomer which is ready to be grafted withthe perfluorinated polyether. The grafting (Step 4) may be accomplishedby hydrolyzing the alkoxy groups of the alkoxysilanes on the crosslinkerand/or the alkoxysilane terminated perfluorinated polyether to providethe compounds of structure I.

Step 1: (Dehydrofluorination)

Step 2: (Regeneration of Amine)

Step 3: (Addition of Amine Across the Double Bond)

Step 4: (Hydrolysis and Condensation)

As described above, the fluoroelastomer crosslinking step may be carriedout in the presence of the perfluorinated polyether. In some suchembodiments, a ratio of the aminofunctionalized silane to thealkoxysilane-terminated perfluorinated polyether is in a range fromabout 0.5:1 to about 3:1, or about 1:1 to about 2:1. In someembodiments, the ratio may be about 1.5:1. In embodiments, an amount ofthe aminofunctionalized silane relative to the fluoroelastomer is in arange from about 2 pph to about 10 pph. In embodiments, the attachmentof the aminefunctionalized crosslinker with the perfluorinated polyethermay be carried out before the crosslinking of the fluoroelastomer. Anyof the steps describe above may be carried out with the aid of acatalyst and reactions may be optionally carried out at elevatedtemperatures. Typically, the reactions will be run in an organicsolvent, such as methyl isobutyl ketone (MIBK). In embodiments, thereactions are all run in a one-pot sequence without isolation ofchemical intermediates. In embodiments, the reaction products is useddirectly to form a coating with or with out any type of purification.

In some embodiments, there are provided inkjet printheads comprising afront face having a polymer coating, the polymer coating comprising anoleophobic grafted polymer comprising a crosslinked fluoroelastomer anda perfluorinated polyether grafted to the crosslinked fluoroelastomer.In some such embodiments, oleophobic grafted polymer comprises thecompound of structure I.

Modeling has shown that the ink contact angle for competent oleophobiccoating should be greater than about 40 degrees over lifespan of thecoating to maintain a drool pressure specification of about 4 inches,with a higher contact angle being more beneficial. The front facecoating ideally also has a low slide angle to enable the easy/self cleanfeature, which will lead to a printhead cartridge with no or lowmaintenance, high engine reliability and low run cost. Low slide angleis a measure of low ink adhesion and indicates that ink can be wiped offcleanly from the surface without leaving ink residue around the nozzle.Any ink residue around the nozzle area can break the ink meniscus andlead to drooling at pressure below the spec value. Also any coatingsideally maintain these properties after harsh fabrication conditions ofthe stacking press i.e., about 290° C. at 350 PSI for 30 min. Thus, inembodiments, the polymer coating has an ink contact angle of at leastabout 50 degrees and an ink slide angle of less than about 30 degrees.Furthermore, the polymer coating employed on the printhead front facemay be characterized by being stable at 290° C. at 350 psi to facilitatemanufacture.

The oleophobic low adhesion surface coating disclosed herein can beemployed as an anti-wetting printhead front face coating for an inkjetprinthead configured to eject ink onto a recording substrate. Anysuitable recording substrate may be employed, including plain paperssuch as XEROX® 4024 papers, XEROX® Image Series papers, Courtland 4024DP paper, ruled notebook paper, bond paper, silica coated papers such asSharp Company silica coated paper, JuJo paper, Hammermill LaserprintPaper, and the like, transparency materials, fabrics, textile products,plastics, polymeric films, inorganic substrates such as metals and wood,and the like.

In some embodiments, the printhead comprises a front face havingdisposed on a surface thereof an oleophobic low adhesion coatingcomprising an oleophobic low adhesion polymeric material wherein jetteddrops of ultra-violet gel ink or jetted drops of solid ink exhibit acontact angle with the surface coating that is greater than about 50degrees. In some embodiments, the contact angle is greater than about55, or greater than about 65 degrees. In one embodiment, there is noupper limit to the contact angle exhibited between the jetted drops ofultra-violet gel ink or jetted drops of solid ink and the surfacecoating. In another embodiment, the contact angle is less than about 150degrees, or less than about 90 degrees. The greater the ink contactangle, the higher the drool pressure. Drool pressure relates to theability of the aperture plate to avoid ink weeping out of the nozzlewhen the pressure of the ink tank (reservoir) increases. In someembodiments, the coatings provide, in combination, low adhesion and highcontact angle for ultra-violet curable gel ink and solid ink whichadvantageously affects the drool pressure. In some embodiments, thecoatings herein provide a low sliding angle of less than about 30degrees. In some embodiments, the sliding angle is less than about 25degrees. In some embodiments, the sliding angle is greater than about 1degree. Contact angle is largely insensitive to drop size. However,contact angle can be measured upon disposing 5-10 microliter drops of UVink or solid ink onto the surface coating. Sliding angle can be measuredupon disposing 7-12 microliter drops of UV ink or solid ink onto thesurface coating.

In embodiments described herein, the oleophobic low adhesion coatingsare thermally stable, thereby providing a low sliding angle in a rangefrom about 1 degree and about 30 degrees and a high contact angle in arange from about 45 degrees and about 150 degrees even after exposure tohigh temperatures (e.g., temperatures in a range from about 180° C. andabout 325° C.) and high pressures (e.g., pressures in a range from about100 psi and about 400 psi) for 15 extended periods of time (e.g.,periods of time in a range from about 10 minutes and about 2 hours). Inone embodiment, the oleophobic low adhesion coating is thermally stableafter being exposed to a temperature of about 290° C. at pressures ofabout 350 psi for about 30 minutes. The fabrication of high densityPiezo printheads requires a high temperature, high pressure adhesivebonding step. Hence, it would be desirable for a fronfface coating towithstand these high temperature and high pressure conditions. Thestability of the oleophobic low adhesion surface coating describedherein at high temperatures and high pressures is compatible withcurrent printhead manufacturing processes.

When coated onto the front face of an inkjet printhead, the oleophobiclow adhesion surface coating exhibits a sufficiently low adhesion withrespect to the inks that are ejected from the inkjet printhead such thatink droplets remaining on the oleophobic low adhesion coating can slideoff the printhead in a simple, self-cleaning manner. Contaminants suchas dust, paper particles, etc., which are sometimes found on the frontface of inkjet printheads, can be carried away from the inkjet printheadfront face by a sliding ink droplet. Thus, the oleophobic low adhesionprinthead front face coating can provide a self-cleaning,contamination-free inkjet printhead.

As used herein, the oleophobic low adhesion coating can exhibit a“sufficiently low wettability” with respect to inks that are ejectedfrom an inkjet printhead when a contact angle between an ink and theoleophobic low adhesion coating is, in one embodiment, greater thanabout 50 degrees, or greater than about 55 degrees.

The oleophobic low adhesion coating disclosed herein can be employed asan oleophobic low adhesion printhead front face coating for an inkjetprinthead of any suitable inkjet printer (e.g., continuous inkjetprinters, thermal drop-on-demand (DOD) inkjet printers, and piezoeletricDOD inkjet printers). As used herein, the term “printer” encompasses anyapparatus, such as a digital copier, bookmaking machine, facsimilemachine, multi-function machine, and the like, which performs a printoutputting function for any purpose.

The oleophobic low adhesion coating disclosed herein can be employed asan oleophobic low adhesion printhead front face coating for an inkjetprinthead configured to eject any suitable ink (e.g., aqueous inks,solvent inks, UV-curable inks, dye sublimation inks, solid inks, etc.).An exemplary inkjet printhead suitable for use with the oleophobic lowadhesion coating disclosed herein is described with respect to FIG. 2.

Referring to FIG. 2, an inkjet printhead 20 according to one embodimentof the 5 present invention includes a support brace 22, a nozzle plate24 bonded to the support brace 22 and an oleophobic low adhesioncoating, such as oleophobic low adhesion coating 26.

The support brace 22 is formed of any suitable material such asstainless steel and include apertures 22 a defined therein. Theapertures 22 a may communicate with an ink source (not shown). Thenozzle plate 24 may be formed of any suitable material such as polyimideand include nozzles 24 a defined therein. The nozzles 24 a maycommunicate with the ink source via the apertures 22 a such that inkfrom the ink source is jettable from the printhead 20 onto a recordingsubstrate through a nozzle 24 a.

In the illustrated embodiment, the nozzle plate 24 is bonded to thesupport brace 22 by an intervening adhesive material 28. The adhesivematerial 28 may be provided as a thermoplastic adhesive can be meltedduring a bonding process to bond the nozzle plate 24 to the supportbrace 22. Typically, the nozzle plate 24 and the oleophobic low adhesioncoating 26 are also heated during the bonding process. Depending on thematerial from which the thermoplastic adhesive is formed, bondingtemperature can be in a range from about 180° C. and about 325° C.

Conventional oleophobic low adhesion coatings tend to degrade whenexposed to temperatures encountered during typical bonding processes orother high-temperature, high pressure processes encountered duringfabrication of inkjet printheads. However, the oleophobic low adhesioncoating 26 disclosed herein exhibits a sufficiently low adhesion(indicated by low sliding angles) and high contact angle with respect toan ink after it has been heated to the bonding temperature. Thus, theoleophobic low adhesion coating 26 can provide a self-cleaning,contamination-free inkjet printhead 20 with high drool pressure. Theability of the oleophobic low adhesion coating 26 to resist substantialdegradation in desirable surface properties (e.g., including low slidingangle and high contact angle) upon exposure to elevated temperaturesenables inkjet printheads having self-cleaning abilities whilemaintaining high drool pressure, to be fabricated using hightemperatureand high pressure processes. An exemplary process of forming an inkjet10 printhead is described with respect to FIGS. 2-5.

Referring to FIG. 3, an inkjet printhead, such as the inkjet printhead20, may be formed by forming an oleophobic low adhesion coating, such asoleophobic low adhesion coating 26 on a substrate 32. The substrate 32may be formed of any suitable material such as polyimide.

In one embodiment, the oleophobic low adhesion coating 26 may be formedon the substrate 32 by initially applying the reactant mixture that, asdescribed above, includes at least one isocyanate and at least oneperfluoropolyether compound. After the reactant mixture is applied tothe substrate 32, the reactants are reacted together to form theoleophobic low adhesion coating 26. The reactants can be reactedtogether by, for example, curing the reactant mixture. In oneembodiment, the reactant mixture is first cured at a temperature ofabout 130° C. for about 30 minutes to about 2 hours followed by a hightemperature post-cure at about 290° C. for about 30 minutes to about 2hours.

In one embodiment, the reactant mixture may be applied to the substrate32 using any suitable method such as die extrusion coating, dip coating,spray coating, spin coating, flow coating, stamp printing, and bladetechniques. An air atomization device such as an air brush or anautomated air/liquid spray can be used to spray the reactant mixture.The air atomization device can be mounted on an automated reciprocatorthat moves in a uniform pattern to cover the surface of the substrate 32with a uniform (or substantially uniform) amount of the reactantmixture. The use of a doctor blade is another technique that can beemployed to apply the reactant mixture. In flow coating, a programmabledispenser is used to apply the reactant mixture.

Referring to FIG. 4, the substrate 32 is bonded to the aperture brace 22via adhesive material 28, resulting in the structure shown in FIG. 5. Inone embodiment, the adhesive material 28 is bonded to the aperture brace22 before being bonded to the substrate 32. In another embodiment, theadhesive material 28 is bonded to the substrate 32 before being bondedto the aperture brace 22. In yet another embodiment, the adhesivematerial 28 is bonded to the substrate 32 and the aperture brace 22simultaneously.

In embodiments where the adhesive material 28 is provided as athermoplastic adhesive, the adhesive material 28 is bonded to thesubstrate 32 and the aperture brace 22 by melting the thermoplasticadhesive at, and subjecting the oleophobic low adhesion 20 coating 26to, a bonding temperature and a bonding pressure. In one embodiment, thebonding temperature is at least about 290° C. In one embodiment, thebonding temperature can be at least about 310° C. In another embodiment,the bonding temperature can be at least about 325° C. In one embodiment,the bonding pressure is at least about 100 psi. In one embodiment, thebonding pressure can be at least about 300 psi.

After bonding the substrate 32 to the aperture brace 22, the aperturebrace 22 may be used as a mask during one or more patterning processesto extend the apertures 22 a into the adhesive material 28, as shown inFIG. 2. The aperture brace 22 may also be used as a mask during one ormore patterning processes to form nozzles 24 a in the substrate 32,thereby forming the nozzle plate 24 shown in FIG. 2. The one or morepatterning processes used to form nozzles 24 a may also be applied toform nozzle openings 26 a within the oleophobic low adhesion coating 26,wherein the nozzle openings 26 a communicate with the nozzles 24 a. Inone embodiment, the apertures 22 a may be extended into the adhesivematerial 28 by a laser ablation patterning process, or the like. In oneembodiment, the nozzles 24 a and nozzle openings 26 a may be formed inthe substrate 32 and the oleophobic low adhesion coating 26,respectively, by a laser ablation patterning process, or the like.

EXAMPLES

Synthesis of an Oleophobic Grafted Polymer (A). Referring to FIG. 6, a17.5% solution of a fluoroelastomer (TECNOFLON® FKM (P 959), SolvaySpecialty Polymers, Alpharetta, Ga.) was made by dissolving in methylisobutyl ketone (MIBK) and about 1 pph by weight FC4430 (3M)and AKF 290(Wacker). (Without being bound by theory, it is believed that thesurfactant may impart compatibility between the fluoroelastomer and therelease layer/oil applied on fuser and it prevents pin holes/fish eyedefect.) Next, an amino crosslinker and FLUORLINK™ S10 (Solvay SpecialtyPolymers, Alpharetta, Ga.) with a mole ratio of 1.5:1 in MIBK were mixedand rolled overnight. It has been observed that keeping the mole ratioconstant and increasing the amount of crosslinker and FLUORLINK™ S10proportionally results in improved low adhesion properties. In thisExample, three different formulations were tried with (1) crosslinker:and FLUORLINK™ S10 (0.86mM:0.57 mM) (2) crosslinker: and FLUORLINK™ S10(1.71 mM:1.13 mM) (3) crosslinker: and FLUORLINK™ S10 (2.56mM:1.70 mM.After 16-18 h, Part B was added into Part A dropwise, as indicated inFIG. 3. Once the addition of Part B to Part A was done, MgO/CaO (9%stock solution in MIBK mixture in the sol was added and the mixtureshaked vigorously for five minutes using a devil shaker and theresulting mixture was poured into molds (6×6 inch) and kept at roomtemperature for 16-18 h. Part of the solution was draw bar coated on apolyimide substrate for surface property measurement. Those were curedat room temperature for overnight and transferred to an oven which waskept at 218° C. for 4 hours. Formulation (3) with increased amount ofEF:FSL10 provided the best surface properties and was further evaluatedfor anti-wetting coating application

Characterization of the Oleophobic Grafted Polymer: TGA decompositionprofile in air shows the coatings are stable until 330° C. (FIG. 7).Coatings were evaluated for surface properties towards hexadecane (whichcan be used as a surrogate for oil) and solid ink. Results are shown inTable 1 below.

TABLE 1 Contact Angle (Sliding Angle) Contact Angle (Sliding Angle)hexadecane (degree) solid ink (degree) Stacking + Stacking + InitialStacking 2 day Initial Stacking 2 day (after 290° C./350 psi/ Inking at(after 290° C./350 psi/ Inking at Coating curing) 30 min 140° C. curing)30 min 140° C. Example (A) 64 (12-15) 63 (20-23) 63 (25-27) 68 (15-19)66 (24-28) 64 (32-35) Control 65 (7-11) 63 (13-15) N.A. 71 (10) 68 (15)60 (20) Coating

As can be seen, the surface properties are comparable to the currentcontrol coating. These coatings maintained high contact angles afterstacking conditions (290° C1350 PSI with Teflon coverlay) whichsimulates press adhesive bonding cycles employed during printheadfabrication. Also stacked coatings maintained high contact angle after 2days at 140° C. with molten CYMK ink. The sliding angles were somewhathigher than a control, but the ink slid cleanly from the surface and itis believed to be sufficiently low to enable easy cleaning in use. Inaddition, this exemplary oleophobic grafted polymer is expected to havethe mechanical robustness desired for the long term performance of thesecoatings. These coatings can be scaled up through flow coatingprocedures and the demonstration of the flow coating using these graftedpolymers has been accomplished.

The fact that these coatings show no oil and have very high thermalstability while maintaining the desired surface properties makes themattractive options for anti-wetting coatings for high definition piezoprint applications.

What is claimed is:
 1. An inkjet printhead comprising a front facehaving a polymer coating, the polymer coating comprising an oleophobicgrafted polymer comprising: a crosslinked fluoroelastomer; and aperfluorinated polyether grafted to the crosslinked fluoroelastomer. 2.The inkjet printhead of claim 1, wherein the oleophobic grafted polymerhas a structure of formula I:

wherein FE is a fluoroelastomer; PFPE is a perfluorinated polyether; Lis a linker; m, n, and o are independently an integer from 1 to 10; eachincidence of R¹ and R² is independently a substituted or unsubstitutedC₁-C₆ alkyl, R³ and R⁴ are independently an optionally fluorinated C₁-C₆alkyl or an optionally fluorinated C₁-C₆ alkoxy.
 3. The inkjet printheadof claim 1, wherein the polymer coating has an ink contact angle of atleast about 50 degrees.
 4. The inkjet printhead of claim 1, wherein thepolymer coating has an ink slide angle of less than about 30 degrees. 5.The inkjet printhead of claim 1, wherein the polymer coating ischaracterized by being stable at 290° C. at 350 psi.
 6. A process formaking an oleophobic grafted polymer coating on a printhead comprising:crosslinking a fluoroelastomer with an aminofunctionalized silane;grafting an alkoxysilane-terminated perfluorinated polyether to thecrosslinked fluoroelastomer to form a oleophobic grafted polymer; andcoating the oleophobic grafted polymer on a printhead front face.
 7. Theprocess of claim 6, wherein the the oleophobic grafted polymer has afinal structure of formula I:

wherein FE is a fluoroelastomer; PFPE is a perfluorinated polyether; Lis a linker; m, n, and o are independently an integer from 1 to 10 eachincidence of R¹ and R² is independently an optionally fluorinated C₁-C₆alkyl, R³ and R⁴ are independently an optionally fluorinated C₁-C₆ alkylor an optionally fluorinated C₁-C₆ alkoxy.
 8. The process of claim 6,wherein the crosslinking step is performed in the presence of thealkoxysilane-terminated perfluorinated polyether.
 9. The process ofclaim 8, wherein a ratio of the aminofunctionalized silane to thealkoxysilane-terminated perfluorinated polyether is in a range fromabout 0.5:1 to about 3:1.
 10. The process of claim 9, wherein an amountof the aminofunctionalized silane relative to the fluoroelastomer is ina range from about 2 pph to about 10 pph.
 11. An inkjet printheadcomprising a front face having a polymer coating, the polymer coatingcomprising a structure of formula I:

wherein FE is a fluoroelastomer; PFPE is a perfluorinated polyether; Lis a linker; m, and o are independently an integer from 3 to 8; n is aninteger from 1 to 10; each incidence of R¹ and R² is independently asubstituted or unsubstituted C₁-C₆ alkyl, R³ and R⁴ are independently anoptionally fluorinated C₁-C₆ alkyl or an optionally fluorinated C₁-C₆alkoxy.
 12. The inkjet printhead of claim 11, wherein the linker Lcomprises a C₁-C₆ alkyl terminating in a functional group capable ofcovalently linking to a terminal hydroxyl functionality group of theperfluorinated polyether.
 13. The inkjet printhead of claim 11, whereinthe fluoroelastomer (FE) is a polymer comprising a monomer unit selectedfrom the group consisting of vinylidene fluoride, tetrafluorethylene,hexafluoropropylene, perfluoromethylvinylether and combinations thereof.14. The inkjet printhead of claim 11, wherein the fluoroelastomer (FE)has a fluorine content of at least about 65 percent.
 15. The inkjetprinthead of claim 11, wherein the fluoroelastomer (FE) has a molecularweight in a range from about 50,000 to about 70,0000 daltons as measuredby gel permeation chromatography.
 16. The inkjet printhead of claim 11,wherein the perfluorinated polyether (PFPE) is analkoxysilane-terminated perfluorinated polyether having an averagemolecular weight in a range from about 1,500 daltons to about 2,500daltons.
 17. The inkjet printhead of claim 11, wherein the polymercoating has an ink contact angle of at least about 50 degrees.
 18. Theinkjet printhead of claim 11, wherein the polymer coating has an inkslide angle of less than about 30 degrees.
 19. The inkjet printhead ofclaim 11, wherein the polymer coating is characterized by being stableat 290° C. at 350 psi.